The sides of the cauldron are steep, thickly covered by ancient volcanic gravel. Around the rim of the massive crater, winds can gust to as much as fifty miles an hour. The panorama from the volcano’s rim is of the seared, scorched Death Valley. Downwards, the slope plummets over five hundred feet to the bottom. There is a trail, but running through the gravel is more fun. Walking it, you have to go sideways to keep your feet. Running, the key is to move in short diagonal bursts, to use the gravel to brake yourself. Don’t start falling, you won’t stop until you hit the bottom, and the gravel is sharp.

This is Ubehebe Crater, Death Valley, California. Open to the general public, there are now long lines of people trudging up and down the switchback trail. But when I first remember being there, some fifteen years ago, only a few people did more than look over the rim. Very few went all the way to the white-silt bottom. My family did climb down into the crater. Ubehebe is a small, extinct volcano, but even so, it terrified me. Those early adventures triggered a fascination with volcanic phenomena that has lasted ever since.

Mythology

Volcanoes are one of the most potent, powerful forces on the Earth. They have crept, over the ages, into our nightmares, our folklore, our speech. Intricate mythologies formed around them. Hephaestus, Pele, Llao, Mafuei, Aetna and Fuji all shook the earth and spewed fire in their rages and passions.

Some mountains have their own mythology, too, becoming gods or forces with their own life, malevolence and force. Even now, villagers pray to Mount Etna for her mercy.

Others were the entrances to Hell, the burial grounds of the gods, or the birthplace of monsters. Often, they were the sites of great battles, most likely because of the great earthquakes that often accompany their eruptions.

History

Recently, supervolcanoes, or megacalderas, have begun to grab attention away from their smaller relatives. Most of the supervolcanoes erupted long before there were humans around to record the event. But one did erupt in modern history, and not all that long ago.

In 1815, Mount Tambora erupted in Indonesia. The magma chamber had been filling and expanding for years, and the pressure finally crested. The resulting explosion measured VEI (Volcanic Explosivity Indicator) 7, the second-highest rating on the scale. The explosion was heard over 1200 miles away, and ash fell as far away as Borneo and Java. The climate-effect was severe enough to kill livestock and crops all across North America and Europe, resulting in the worst famine of the 19th century. The following year was known as the ‘Year Without a Summer’.

Tambora’s death-toll was more than 71,000 people. Before the explosion, the peak towered 14,000 feet into the air, and after, just over 9000 feet. The material ejected was estimated to measure more than 160 cubic kilometers.

(In contrast, Mount Saint Helens lost about 1300 feet of its height, killed 57 people, and ejected less than 3 cubic kilometers of debris and ash.)

The Yellowstone hotspot has not erupted for many thousands of years. But, when it did, it may have triggered the basalt floods that covered vast distances in the Pacific Northwest. The calderas of the numerous Yellowstone eruptions dot the landscape. Magma is again building beneath the crust.

The Aira Caldera, in Japan, has also been dormant for a very long time, except for a smaller, active volcano within its caldera. The explosion of this smaller volcano turned the island into a penninsula. The reach of the original caldera was many times larger.

Science

Volcanoes are rated by the Volcanic Explosivity Index (VEI), on a scale of 1-10. Mount Saint Helens rated a low VEI5. Krakatoa and Mount Pinataubo rated VEI6. Supervolcanoes have VEI7 and VEI8 ratings. VEI7 eruptions are four times as big as VEI6. VEI8 eruptions are ten times the size of a VEI7.

Of course, the geographical position of a volcano can influence its effects. Some of the most closely-watched volcanoes right now aren’t supervolcanoes, but their potential for desctruction and loss of life in the short-term is nearly as high. The real danger of a supervolcano is in its wide reach and long-lasting effect.

The fallout from a supervolcano spreads for thousands of miles. Ash, gas and debris get caught in the wind-stream. Such an explosion can trigger a mini-ice age, as massive portions of the world are shrouded in the ash cloud. Famine and disease typically follow as well, leaving the final death-toll of VEI7 or VEI8 eruption much more wide-spread than most volcanoes.

These monsters are a relatively new discovery, and scientists still have more questions than answers.

Recently, scientists discovered a ‘fossil’ supervolcano in the Italian Alps, during seismic shifts. The study of the Sesia Valley caldera could shed valuable light on the lifespans and effects of supervolcanoes.

A supervolcano forms where magma pools under the crust, but cannot break through. As pressure builds, the chamber expands, often doming the surface above it. This process can take hundreds of thousands of years, the magma flowing directly from the mantle in huge ‘plumes’. Finally, the explosion occurs, blowing away the crust above it and releasing massive basalt floods, as well as clouds of ash, volcanic debris and poisonous gases.

There are only a handful of known supervolcanoes, mostly concentrated in a few continents. The Yellowstone, Long Valley and Valles Caldera in the United States, Lake Toba in Indonesia, Taupo Volcano in New Zealand and the Aira Caldera in Japan. A recent discovery added the Vilama Caldera in Argentina, a site which might prove to hold several supervolcanoes.

Although each of these has only exploded a few times, the resulting blasts were enough to blanket vast areas with ash, destroy native lifeforms, and trigger mini ice ages.

The Yellowstone hotspot has received more attention lately than most of the other calderas, due to recent earthquake swarms. The North American Plate lies over the massive Yellowstone Hotspot. Over the past 17 million years, over 142 eruptions have occurred in the hotspot, each forming a caldera. With the movement of the plate, those calderas litter a path from the Oregon-Nevada border (oldest) to the Yellowstone Plateau (newest).

The Yellowstone hotspot is the source of a great deal of controversy and speculation. It appeared on the geologic time-line with a (relative) abruptness. The exact formation and cause of it is not known.

Supervolcanoes have the power to transform the entire geology, climate and civilization of the Earth. They’ve done it before! Think of them as gigantic natural terraforming mechanisms. Supervolcanoes can send hundreds to thousands of cubic kilometers of ash and debris into the atmosphere. Entire species have been wiped out by them before, and the population of the human race severely pruned by the more recent massive explosions.

Fiction

The term ‘supervolcano’ actually appears to owe its use to modern media. In 2000, BBC introduced the term to the general public in the popular-science television series, Horizon. That was the first time that the general public heard about the massive, rare volcanoes.

Spectacular, unpredictable, uncontrollable and deadly, even ‘regular’ volcanoes fascinate both scientists and the casual observer alike. In Science Fiction, volcanoes maintain a steady role as apocalyptic scenarios, catalysts and antagonists. Of the many disasters, weapons and monsters available to us, as writers, volcanoes are possibly one of the most familiar in mechanics and science to the typical reader.

Even the words surrounding the events of a volcanic explosion sound like something out of a science-fiction or fantasy novel. Pyroclastic flow. Ballistic fragment. Base surge. Fumarole. Harmonic tremor. Lahar.

Speculation and Extrapolation

There isn’t much extrapolation to do with this one. Supervolcanoes are one of the most powerful, deadly forces of nature. They can’t be controlled, predicted, caused or stopped. They simply happen, and, with any luck, we’ll get a few weeks or months of warning.

Speculation? Oh, there’s plenty of that.

1.) The threats of Yellowstone’s imminent eruption causes a mass panic. Everyone in the fallout range of the megacaldera puts their homes on the market for a fraction of the original worth, and stampedes east. Entire cities stand completely empty. The economy shatters on this pre-disaster refugee wave.

2.) The Aira Caldera erupts in Japan after a series of massive earthquakes. Japan is decimated, although about half of the population made it out. China and Korea are badly effected, with results ranging from broken damns to falling buildings. With the political structure of the East in jeapordy, the UN has a political crisis on its hands.

3.) A mad scientist figures out a way to trigger one of the supervolcanoes. He then either does so, or holes up and holds the world hostage, triggering a couple of VEI4′s, just to make his point.

4.) Yellowstone blows. East and West are cut off by the resulting ash-clouds and lava flows. Roads are impassable, communications no longer available. The economy is destroyed. The two halves gather themselves and form their own, independent nations.

5.) I’ve got to throw a fantasy one in here! There really are gods in the volcanoes. Unfortunately, they have the mindsets of toddlers. Apocalypse by two-year-old supergod.

In theory, we could punch a hole in the magma chamber to let out the pressure before it builds up. There would be very interesting wrangles over doing so now (and wrecking property values in the neighborhood as you get a volcano in the back yards of existing property owners) vs. later (after all, it might not erupt in this generation).

Volcanoes are my one true phobia. I first read your post in pieces over the course of a day, but it still gave me the shaking sweats. Psychologically speaking, I’d prefer an asteroid hit. There is just something very wrong about volcanoes… The ground we stand on should not rise up and destroy us! I mean really, if you can’t depend on rocks–? *shakes*

Furthermore, how badass are we compared to supervolcanoes? Heh, not very.